Best test for subacute cutaneous lupus erythematosus is

Cutaneous lupus erythematosus encompasses a wide range of dermatologic manifestations, which may or may not be associated with the development of systemic disease. Cutaneous lupus is divided into several subtypes, including acute cutaneous lupus erythematosus, subacute cutaneous lupus erythematosus, and chronic cutaneous lupus erythematosus. Chronic cutaneous lupus erythematosus includes discoid lupus erythematosus, lupus erythematosus profundus, chilblain cutaneous lupus, and lupus tumidus. Diagnosis of these diseases requires proper classification of the subtype, through a combination of physical exam, laboratory studies, histology, antibody serology, and occasionally direct immunofluorescence, while ensuring to exclude systemic disease. Treatment of cutaneous lupus consists of patient education on proper sun protection along with appropriate topical and systemic agents. Systemic agents are indicated in cases of widespread, scarring, or treatment-refractory disease. Subacute Cutaneous Lupus Erythematosus (SCLE) occurs primarily in young to middle aged women . SCLE is highly photosensitive, with 70-90% of patients meeting the ACR definition of abnormal photosensitivity . There are two morphologic variants of SCLE: annular and papulosquamous An estimated 50% of SCLE patients meet criteria for SLE . Patients with SCLE usually have only mild systemic symptoms, most commonly ahritis and myalgias, while severe systemic symptoms, such as lupus vasculitis, CNS lupus, and nephritis occur in less than 10% . Immunologically, 70% of SCLE patients are anti-Ro (SS-A) positive, and overlap between Sjogren's syndrome and SCLE has been seen . Ref - Davidson 23rd edition pg 941